Fixture for forming gear cutters



April 8, 1944. H. FELPHREY 2,346,866

FIXTURE FOR FORMING GEAR CUTTERS Filed Oct. 29, 1940 ZSheets-Sheet 1 April 18, 1944. v H P R Y 2,346,866

FIXTURE FOR FORMING GEAR CUTTERS Filed Oct. 29, 1940 2 Sheets-Sheet 2 INVENTOR /dgYry g l wire A RNEYi Patented Apr. 18, 1944 FDITURE FOR FORMING GEAR CUTTERS Harry Pelphrey, Detroit, Mich., assignor to Michigan Tool Company, Detroit, Mich.,'a corporation of Delaware Application October 29, 1940, Serial No. 363,330

Claims.

The present invention relates to forming gear cutters, and particularly relates to a fixture for generating the cutting form of a gear cutter.

One of the primary objects of the present invention is to provide a fixture by which a cutter may be readily and accurately formed in which the cutting portion is elongated and i of a shape conforming to the shape of the entire interdental space of the teeth of the gear to be cut.

Another object of the invention is to provide a fixture by which an element of the contour and shape of an internal helical gear tooth is generated by grinding.

Another object of the invention is to provide a fixture by which an element to be formed is supported in a predetermined position with respect to a rotating grinding element and is then guided in predetermined paths while in such engagement to form a shape corresponding to the shape of the interdental space between the teeth of an external gear, in which the paths are predetermined from the characteristics of the gear, such as'the base helix angle, the lead, the base radius, and/or other characteristics.

Other objects of the invention will become apparent from the following specification, the drawings relating thereto and from the claims hereinafter set forth.

In the drawings, in which like numerals are used to designate like parts in the several views throughout:

Figure 1 is a fragmentary, front perspective view of a fixture embodying features of the present invention;

Fig. 2 is a rear perspective view of the structure shown in Fig. 1;

Fig. 3 is a top plan view of the structure shown in Fig. 1;

Fig. 4 is an enlarged, side elevational view, with parts in section, showing the cutting tool mounted therein in elevation;

Fig. 5 is an enlarged plan view taken substantially along the line 5-5 of Fig. 4; and

Fig. 6 is an enlarged, fragmentary, cross-sectional view taken substantially along the line 6-6 of Fig. l.

The fixtufe of the present invention is adapted for forming gear cutters such as those disclosed and claimed in the copending application of Harry Pelphrey, Serial No. 363,329, filed October 29, 1940, which are used in the machine disclosed and claimed in the copending application of Harry Pelphrey, Serial No. 363,331, filed October 29, 1940.

The fixture is so constructed that a gear cutter is generated in a simplified and accurate manner by forming thereon a cutting portion having the shape of an internal involute gear, or having the shape of the entire interdental space between the teeth of an external gear to be cut by the cutters. In the fixture, which is illustratively disclosed and which will be described in detail hereinafter, the cutter being formed is for cutting an external helical involute gear. I

Referring to the drawings, the element or gear cutter being-formed is indicated at Ill. The fixture comprises a base, or standard l2, which may be supported above the floor in the usual way. The standard l2 .also includes an upright bracket it upon which the means for removing the stock to provide the cutting form is mounted. In the embodiment illustrated, such means includes a disc-shaped grinding element l6 which is fixedly mounted on the lower end of a vertical shaft l8. Such shaft I8 is suitably supported within suitable mounting means in the usual way, and is rotated by means of a conventional drive, such as that disposed within the housing 20, which may be fixed tothe bracket [4.

Th peripheral edge of the grinding element It is formed on a radius which is less than the smallest radius of curvature of any portion of the surfaces formed on the gear cutter.

A base 22 is set upon the top horizontal surface of standard I2 and is fixed thereto by means of suitable bolt 24, which are fixed to the standard i2 and which engage clamping elements 26. Such clamping elements 26 engage within suitable apertures 28 in the side walls of base 22 to clamp the base to the table. It is pointed out that such base may be adjustably fixed to the table for varying its angular position with respect to grinding disc l6, for reasons that will be pointed out in detail hereinafter. It will also be appreciated that the members 24 and 26 may be suitably disposed on the standard l2 and that a I suitable number may be provided for adjustably fixing the base 22 to the standard l2.

The base 22 includes a top horizontal portion 30 upon which a horizontal member 82 is slidably mounted. A longitudinally extending guideway 7 which is fixed to the sides of member 32 along each side thereof. Each of such members 48 is provided with inwardly facing V-shaped portion; 42. It will thus be seen that the facing portions 86 and form guideways on each side of the member 32 within which the ball bearings 38 are received. The member 32 may thus be slid longitudinally with respect to the base 22.

An upstanding U-shaped bracket 44 is fixed to the top surface of member 82. The ends 45 of the bracket 44 have bearing 46 mounted therein in alignment with each other. A shaft 44 is disposed within the brackets 46 and projects beyond both sides thereof. That portion of the shaft between the sides 45 of the bracket is formed with spiral or helical grooves 58 therein, which provide a spiral or helical rib 52 integral with the shaft 48. The grooves 58 and the rib 52 are formed with the lead corresponding to that of the gear to be cut by the cutters formed with the present fixture.

The rearwardly projecting end of the shaft 48 has a hand wheel 54 fixedly connected thereto, so that such shaft may be turned in either direction by turning the wheel 54.

An upstanding follower bracket 56 is fixedly mounted on the base 22 ina position adjacent the spiral guide 52. A stub shaft 58 is mounted in the upper end of the bracket 58 and has a follower in the form of a roller 68 pivotally fixed to the forward end thereof. Such roller 68 is adapted to bear against one of the sides of the spiral rib 52. Another roller 82 is mounted on one end of an arm 64; and such roller 62 is adapted to engage the other side of the spiral guide rib 52. The arm 64 is pivoted intermediate its ends by means of a suitable pivot pin 66 to the member 58. The opposite end of the member 84 is engaged by a spiral spring 68, which may have the opposite end thereof fixed to a pin 18, which in turn is mounted on a plate 12. Such plate 12 may be suitably fixed to the bracket 56. The spring 68 is in tension, so that it will be seen that roller 62 is resiliently urged against the spiral ide rib 52.

It will thus be seen that the bracket 56 is fixed with respect to the base 22, and that the bracket 44 is fixed with respect to the table 82. By turning the wheel 54, the shaft 48, together with the guide rib 52, is correspondingly turned so that the engagement of the guide rib 52 with the rollers 68 and 62 causes the member 32, together with the bracket 44, to slide with respect to the table 22.

The cutter I8 is supported within suitable mounting means on the forwardly projecting end of shaft 48, and such mounting means include a member I4 having a vertical portion I6 and a horizontal forward portion I8. The vertical portion I6 is provided with a horizontal opening therethrough through which the reduced end portion of shaft 48 extends. Such shaft is fixedly connected to members I4 by suitable keys or the like, so that it will be seen that the member I4 rotates upon rotation of shaft 48 and also moves with table 82.

An upstanding holding block 88 :is fixedly mounted on portion I8 and is adapted to receive therein the cutters I8. Such member 88 is provided with an aperture 82 therethrough, having a shape defined by sides 83 84, 85, 86, 81 and 88 (Fig. 5). It will thus be seen that the aperture is in its major portion rectangular in shape with the two oppositely disposed corner portions, so that the tool I8 may be reversed within the aperture in order to generate opposite sides thereof. The tool in transverse section is in the form of a right angle trapezoid, and is adapted to be snugly received within the aperture 82, as shown in Fig. 5. The aperture 82 is offset from the vertical or from the axis of rotation of the grinding element I6 at the end clearance angle of the tool.

The longitudinal center line of the block 88 is parallel to the axis of shaft 48. The longitudinal center line of the aperture 82, within which the tool I8 is disposed, and the longitudinal center line of a right section of the tool I8 are disposed at a predetermined angle with respect to the longitudinal center line of the block 88. Such angle is indicated at A, in Fig. 5, and in the embodiment illustrated is approximately the out-. side helix angle of the gear to be cut. The outside helix angle is preferred in order to get as thin a blade as possible but still have the complete form generated. According to the broader aspects of the present invention the helix angle on the base or pitch circles could be used, but this would necessitate a thicker cutting tool.

As mentioned above, the axis of shaft 48 is disposed at a predetermined angle with respect to a tangent with disc I6 at the point of contact of the tool I8 therewith. Such predetermined angle in the embodiment illustrated is approximately the base helix angle of the gear to be cut.

The peripheral edge of the disc I8, which is contacted by the cutter I8, is disposed a predetermined distance below the axis of shaft 48; and such predetermined distance is the base radius of the gear to be cut. The tip of the tool I8 is disposed a distance substantially equal to the root radius of the gear to be cut from the axis of shaft 48.

As the wheel 54 is turned, the tool I8 is turned with holder 82, in engagement with the disc IS, on the base radius of the gear to be cut, and at the same time the holder is moved along a straight line toward the disc I6, such straight line being parallel to the axis of shaft 48 and, consequently, being at approximately the base helix angle with respect to a tangent to the wheel at the point of contact. A line, corresponding to the helix or the lead of the gear to be cut, is thus generated on the tool I8.

The standard I2 includes a base portion 82, having'upwardl'y disposed ways 84 formed in the top surface thereof. Such ways 84 are parallel to each (other and engage with complementa'ry portions of a slidable table 86, which also forms part of the base or standard 12. The member 22 is fixedly secured to the slidable table 86 of the standard I2.

A hand-wheel 88, having a screw (not shown) associated therewith, is mounted on the base 82, and the screw co-operates with a nut (not shown) mounted on the underside of member 95. It will thus be seen that by turning the handwheel the member 86 is moved longitudinally with respect to the base 82, so that the members 22, 32, together with the holder 88 and tool I8. are bodily shifted with respect to the grinding disc I6, as shown by broken lines in Fig. 3.

By bodily shifting such member 86, the point of contact of thedisc I6 on tool I8 is changed so that by shifting the table'in increments and rotating the wheel 54, a plurality of the lines mentioned above in connection with the rotary and reciprocatory movement of the holder 88 with respect to the disc are generated to provide the involute form on one side of the tool I8. When such from is generated, the tool I8 is reversed within aperture 82, and the process is repeated to generate the involute form on the opposite side of the tool.

A fiat, indicated at 99, is ground at an angle normal to the helix of the cutting portion of the tool ill with the desired angle of rake, and the cutter is thereby completed. When it is desired to sharpen the cutter, it ismerely necessary to grind down the fiat 99 at corresponding angles.

Formal changes may be made in the specific embodiment of the invention described without departing from the spirit and substance of the invention, the scope of which is commensurate with the appended claims. l

What is claimed is:

1. A machine for forming an element havin the shape of an internal helical gear tooth comprising a standard, a rotatable grinding element mounted on said standard, a holder torsupporting said first-named element, meansf mounting said holder for rotary and reciprocatory movement about an axis disposed at substantially a right angle with respect to the axis of rotation of said grinding element, said axis of rotation and reciprocation of said holder being disposed at a predetermined angle with respect to a tangent at a point of contact of the element being formed with the periphery of the grinding element, said predetermined angle being the base helix angle oi. said gear, means mounting said last named means and said grinding element for relative movement toward and away from each other, and means mounting said first named element in said holder adj acent said grinding element, said holder being so constructed and arranged that said first-named element is disposed on the side of said grinding element opposite to that of said axis of rotation and reciprocation.

2. A machine for forming an element having the shape of an internal helical gear tooth comprising a standard, a rotatable grinding element mounted on said standard, a holder ior supporting said element, means mounting said holder for rotary and reciprocatory movement about an axis disposed at substantially a right angle with respect to the axis or rotation of said grinding element, means mounting said last named means and said grinding element for relative movement toward and away from each other, and said holder being constructed to support said first named element at a predetermined angle with respect to said axis of rotation and reciprocation and in a position disposed on the side of the grinding wheel opposite to that of said axis of rotation and reciprocation, said predetermined angle being the outside helix angle of said gear.

3. A machine for forming an element having the shape of the interdental space between the teeth of anextemal gear comprising a standard, a rotatable grinding element mounted on said standard, the peripheral edge or said grinding element having a cross-sectional curvature of a radius less than the radius of the curvature of the surface of the element being formed, a holder for supporting said first named element, means mounting said holder for rotary and reciprocatory movement about an axis disposed substantialiy at a right angle with respect to the axis oi so constructed and arranged that said firstnamed element is disposed on the side 01' the grinding element opposite to that of said axis 01' rotation and reciprocation.

4. A machine for forming a gear cutter having the shape of the interdental space between the teeth of an external gear comprising a standard. a rotatable grinding element mounted on said standard, a holder for supporting said cutter, means mounting said holder for rotary and reciprocatory movement about an axis disposed at substantially a right angle with respect to the axis of rotation of said grinding element, the axis of rotation and reciprocation of the holder being spaced from the peripheral edge of the grinding element a distance substantially equal to the base radius of said gear and being disposed at a predetermined angle with respect to a tangent at the point of contact of the element being formed with the periphery of the grinding element, said predetermined angle being the base helix angle of said gear, means mounting said last named means and said grinding element for relative movement toward and away from each other, and means mounting said cutter in said holder adjacent said grinding element, said holder being so constructed and arranged that said cutter is disposed on the side of the grinding element opposite to that of said axis of rotation and reciprocation.

5. A machine for forming the shape 01' the interdental space between the teeth or an external helical gearalong an elongated end or an element comprising astandard, a rotatable grinding element mounted on said standard, a holder for supporting said first named element, means mounting said holder for rotary and reciprocatory movement about an axis disposed at substantially a right angle with respect to the axis of rotation of said grinding element, the axis of rotation and reciprocation of said holder being disposed at a predetermined angle with respect to a tangent at the point of contact of the element being formed with the periphery of the grinding element, said predetermined angle being the base helix angle or said gear, means mounting said last named means with said grinding element for relative movement toward and away from each other, and said holder being constructed to support the elongated end or said first named element at a predetermined angle with respect to said axis of rotation and reciprocation and in a position disposed on the side or the grinding wheel opposite to that of said axis of rotation and reciprocation, said last named predetermined angle being the outside helix angle of said gear.

HARRY PELPHREY. 

